The present invention relates to odor collection and analysis and, more particularly, to apparatus for collecting large odor samples and for storing the odor samples for an extended period before analysis.
The analysis of odor components is complicated by the small quantities of volatile components in the headspace of an object whose odor is to be collected and analyzed. The amounts are generally in the sub-microgram range. Thus, some method of concentrating the odor components over a period of time is desirable. One method of concentrating the odor components includes drawing air, or an inert carrier gas such as nitrogen or hydrogen over the object and passing the gas containing the odor components through an adsorptive material such as Tenax. Normal laboratory procedures also include removal from the gas stream of water vapor using a cold trap or a water absorbent such as CaCl.sub.2 and a suitable trap for carbon dioxide. The odor components adsorbed in the adsorptive material is desorbed and analyzed by conventional gas or liquid chromatography.
Another prior art device for odor collection and analysis consists of a fused silica fiber coated with an adsorptive material that adsorbs odor components either directly from the headspace of an object or from the air space of an object confined in a container. The fiber is then heated to desorb the components, which may be analyzed by conventional gas chromatography. The same device can also be used to adsorb organic components from a solution. The adsorbed species then can be either thermally desorbed for analysis by gas chromatography or solvent desorbed for analysis by conventional liquid chromatography. In both cases the main deficiency of the silica fiber device is its limited sample capacity (in the nanogram range of amounts).
Another device uses a "plastic" bag to enclose an object (e.g., a flower) whose odor is to be collected for a period long enough to obtain measurable levels of odor components. The object is removed from the bag, and the bag is squeezed to expel odor components into an adsorbent material such as Tenax. The adsorbed components then can be desorbed for analysis by gas or liquid chromatography.
The bag technique has four principal disadvantages when it is employed in the field to capture odor components. First, many types of plastic used for this purpose may be at least slightly permeable, thereby permitting loss of some odor components or infiltration of outside contaminants, or both. Second, the polymer may contaminate the odor components with outgassed components of its own. Third, since the bag must be large enough to contain the entire object, there is a size and portability problem when it is desired to collect a large number of samples of odors in a field trip. Finally, it is often desirable to return the bag with its contained object to the laboratory for multiple analyses. This becomes a difficult to impossible task when it is necessary to transport bagged samples across national boundaries.
Although the preceding and ensuing disclosure uses the words "odor components" to describe the techniques being employed, it must be understood that the invention is not limited to collection and analysis of odors. The invention must be seen as relating to collection and storage of any chemical component, and the delivery of that component for analysis, whether or not such chemical component is an olfactory stimulant. The present disclosure is cast in the environment of gaseous components. However, the apparatus and methods discussed herein are equally applicable to sorption of chemical components from a liquid, and also to desorption into a liquid medium which may then be subjected to analysis using, for example, liquid chromatography.